The primary goal of this research project is to establish the significance of Herring bodies anddpituicytes in the secretory activity of peptidergic neurosecretory neurons. For that purpose, the fate of 35S-cysteine labeled neurosecretory granulated vesicles will be studied during and following induced localized temporary or permanent arrest of axoplasmic transport (experimental induction of Herring bodies) in the infundibulum of the frog; furthermore lysosomal activity, transport of extragranular hormones and retrograde transport of HRP within the well developed axonal endoplasmic reticulum of neurosecretory axons will be investigated. The significance of Herring bodies will be further studied through the investigation of ultrastructural changes occurring in the empty Herring bodies consistently present in the rat hypophysial stalk following dehydration, rehydration and colchicine administration. Finally, the ontogenic development of pituicytes will be studied in the rat at the ultrastructural level.